<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>观察者模式</title>
</head>
<body>
    <script>
        //发布者-目标
        class Dep{
            constructor (){
                //记录所有订阅者
                this.subs = []
            }
            //添加订阅者
            addSub(sub){
                if(sub&&sub.update){
                    this.subs.push(sub)
                }
            }

            //发布通知
            notify(){
                this.subs.forEach(sub=>{
                    sub.update()
                })
            }
            
        }

        //订阅者-观察者
        class Watcher{
            update(){
                console.log('update');
            }
        }

        //测试
        let dep = new Dep()
        let watcher = new Watcher()
        dep.addSub(watcher)

        dep.notify()
    </script>
</body>
</html>